The Russian navy is about to stage its largest war exercise in a long time — possibly the largest since before the breakup of the Soviet Union. It’s a chance for President Vladimir Putin to show off his military might, of course. But the exercise may also be a subtle warning to the United States: Stay clear of waters that traditionally lie in Russia’s sphere of influence.

The Russian defense ministry says its the “first time in decades” it’s launched naval exercises on this scale. The drills involve warships from all of Russia’s fleets: “the Northern, Baltic, Black Sea and Pacific,” noted a statement from the ministry. The exercise will be reportedly held in late January, and involve amphibious landings in the Caucasus and naval exercises in the Mediterranean.

Russia’s T-50 stealth fighter prototype, the first radar-evading warplane outside the U.S. when it debuted in January 2010, is slightly less stealthy than the American F-22 and about equal to the smaller F-35. But in several other respects the new warplane from the Russian Sukhoi design bureau is actually superior to the American models.

That’s the surprising conclusion of the first-ever public scientific analysis of the T-50′s Radar Cross-Section (RCS), complete this week by Dr. Carlo Kopp, an analyst with the independent think tank Air Power Australia.

“The shaping of the T-50 is inferior to that of the F-22 Raptor,” Kopp writes in his dense, jargon-heavy report. But the F-35 and T-50, he adds, exhibit “similar … RCS behavior.”

But Kopp’s assessment of the T-50 comes with caveats. Quite a few of them, actually. To match the stealthiness of the Lockheed Martin F-35 — to say nothing of the company’s F-22 — Sukhoi’s engineers will have to, among other changes, modify the T-50′s engines to a less obtrusive fitting and add a layer of radar-absorbing material to the plane’s skin.

Ever since a protest movement fueled in part by social media erupted to challenge Vladimir Putin’s re-ascension to the Russian presidency, several opposition figures have found themselves arrested, charged and facing lengthy prison sentences. Only the latest one actually tweeted his own arrest and interrogation.

“I am being taken in for questioning by the SK,” protest leader Sergei Udaltsov tweeted on Wednesday, referring to the Russian equivalent of the FBI, the State Investigative Agency. Hours before, he announced on Twitter that his apartment had been raided. His computer was reportedly seized along with documents and cash. Elsewhere police raided the homes of his assistant, Konstantin Lebedev; and Ilya Ponomaryov, an assistant to a lawmaker in the Just Russia opposition party. Then he tweeted: “Brought to the SK. We are waiting for a lawyer to start questioning.” Several more tweets followed, including one: ”Do not be silent!”

Tweets from him, at least, went silent for hours after that. Instead, his Twitter account began retweeting messagesfrom activists who had spoken with Udaltsov on the phone. They learned Udaltsov had been placed under house arrest. Late Wednesday, he was released: “Friends! My way out of the UK on bail – much your merit. Thanks for your support! Now we must fight for Lebedev!” he tweeted. His supporters have also since created a Facebook group to organize a protest set for Saturday. Protest leader Alexei Navalny — perhaps Russia’s most popular blogger — also kept tabs on the group. “What did they do? What crime was committed? Where is the evidence? Where, at least, common sense?” he blogged.

China’s newest stealth fighter prototype is made in the People’s Republic and could pose a challenge to U.S. air power. But it’s got an Achilles’ Heel: its engines are Russian imports.

Without reliable, homemade motors, China’s planned stealth armada will continue relying on Russian-made engines that aren’t always adequate — and in any event can be withheld by a wary Moscow.

“China’s inability to domestically mass-produce modern high-performance jet engines at a consistently high-quality standard is an enduring Achilles’ Heel of the Chinese military aerospace sector,” wrote Andrew Erickson, a Naval War College analyst. Erickson chalked up the engine gap to a lack of standardization, cooperation and quality control in Chinese industry.

The new J-21, which apparently hasn’t flown yet, first appeared over the weekend in photos snapped at the Shenyang Aircraft Corporation’s factory airfield in northeast China. One high-rez pic clearly featured the twin-tail fighter’s two engines. “A good early guess is that the engines are Klimov RD-93s,” ace aviation reporter Bill Sweetman concluded.

The RD-93, a derivative of the engine fitted to Russia’s classic MiG-29 fighter, also powers China’s Chengdu JF-17, a light fighter intended for export. China bought at last 100 RD-93s from Russia starting in 2005. It seems at least two wound up with Shenyang for its new stealth fighter prototype.

Just one problem: The new drones won’t be ready for combat until 2040 at the earliest, Zhikharev told Russian news agency RIA Novosti. That’s a full two decades after the U.S. plans to deploy its own jet-propelled, armed unmanned aerial vehicles.

This week we highlighted the U.S. military’s small force of Soviet- and Russian-made MiG and Sukhoi fighters, studied for intelligence and flown for realistic air combat training. Now Bryan William Jones provides us some photos of the American MiGs at the Threat Training Center at Nellis Air Force Base in Nevada.

In recent years, the US government has created research agencies for homeland security, intelligence, and energy — all modeled on the Pentagon’s mad-scientist arm, Darpa. Now Russia has gotten the bug, too.

Russian industry and defense leaders announced plans last week to bankroll the Russian Foundation for Advanced Research Projects in the Defense Industry. Russia’s newly re-coronated president, Vladimir Putin, has already sent a bill to parliament to authorize the agency, which will be tasked with keeping track of projects that “can ensure Russian superiority in defense technology,” according to news service RIA Novosti.

One possible location is near the Gromov Flight Research Institute — an experimental aircraft test base — to Moscow’s southeast. The future site, though, may also resemble the Skolkovo Innovation Center, a sort of Silicon Valley for Russia’s high-tech companies located on the city’s opposite end. But instead of focusing on civilian IT and biotech like at Skolkovo, the companies near Gromov would take charge of “all high-risk and fundamental research projects in the military-industrial complex,” Dmitry Rogozin, chief of Russia’s defense industry, said.

Kadyrov also apparently had a problem with Twitter impostors. A statement from the Chechen government said the account is official, and “has nothing to do with other accounts in social networks attributed to the head of the Chechen Republic.”

A transport ship the U.S. believes is carrying attack helicopters to Syria is now heading back to Russia. Ostensibly, the MV Alaed turned around after its insurance coverage was pulled. But the ship’s return coincides with a meeting between Obama and Vladimir Putin — a sign the two leaders may be starting to cooperate on what to do about Syria’s deadly war.

According to press reports, the Alaed, with its load of Mi-25 attack helos, had its insurance yanked by its British insurer, Standard Club, on Monday. The insurer had been reportedly approached by British security services and informed that providing insurance to the Alaed, which is owned by Russian cargo line Femco, violated European Union sanctions prohibiting arms sales to Syria. The insurer pulled its coverage, and the ship then turned back toward the Russian port of Kaliningrad. The ship had earlier stopped about 50 miles off Scotland’s northwest coast.

“The foreign secretary made clear to Russian foreign minister [Sergey] Lavrov when they met on 14 June that all defence shipments to Syria must stop,” a British Foreign Office statement read. The Foreign Office added that it is “working closely with international partners” to “stop the Syrian regime’s ability to slaughter civilians being reinforced through assistance from other countries.”